Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$237.60	11.431%	$264.7601	$264.76	$264.75	$264.80
Purchase #2	$157.69	3.108%	$162.591	$162.59	$162.60	$162.60
Purchase #3	$127.46	13.774%	$145.0163	$145.02	$145.00	$145.00
Purchase #4	$206.36	6.316%	$219.3937	$219.39	$219.40	$219.40
Purchase #5	$233.99	4.778%	$245.17	$245.17	$245.15	$245.20
Purchase #6	$65.75	9.282%	$71.8529	$71.85	$71.85	$71.90
Purchase #7	$101.60	10.160%	$111.9226	$111.92	$111.90	$111.90
7 purchase totals =	$1,130.45		$1,220.7066	$1,220.70	$1,220.65	$1,220.80